The temporal dynamics of individual colour-space geometries in the human brain

We often assume that people see the world in a similar way to us, as we can effectively communicate how things look. However, colour perception is one aspect of vision that varies widely among individuals as shown by differences in colour discrimination, colour constancy, colour appearance and colour naming. Further, the neural response to colour is dynamic and varies over time. Many attempts have been made to construct formal, uniform colour spaces that aim to capture universally valid similarity relationships, but there are discrepancies between these models and individual perception. Combining Magnetoencephalography (MEG) and psychophysical data we examined the extent to which these discrepancies can be accounted for by the geometry of the neural representation of colour and their evolution over time. In particular, we used a dense sampling approach and collected neural responses to hundreds of colours to reconstruct individual fine-grained colour-space geometries from neural signals with millisecond accuracy. In addition, we collected large-scale behavioural data to assess perceived similarity relationships between different colours for every participant. Using a computational modelling approach, we extracted similarity embeddings from the behavioural data to model the neural signal directly. We find that colour information is present in the neural signal from approximately 70 ms onwards but that neural colour-space geometries unfold non-uniformly over time. These findings highlight the gap between theoretical colour spaces and colour perception and represent a novel avenue to gain insights into the subjective nature of perception.